The invention relates to a multilayer body as well as a method for producing a multilayer body.
This is in particular a multilayer body in which, by an arrangement of electrically conductive material in a layer on a carrier, an item of information is encoded which is capacitively readable.
The multilayer body can be formed in particular in the form of a transfer film, a laminating film or a security thread. The multilayer body can be applied to or integrated into a plurality of different substrates, in particular banknotes, credit cards, identification documents, passports, tickets, travel and admission tickets, travel documents, product packaging, tags, playing cards etc.
Thus it is known from WO 2011/154524 A1 to provide several electrically conductive areas (so-called coupling surfaces), which are all galvanically coupled to each other via conductive traces in one embodiment example, on a substrate which can comprise paper, but also plastic. The size of the electrically conductive areas is chosen to match measuring fields of a reader. In particular this is a reader with a touch panel functionality. When the substrate with the electrically conductive areas is positioned, there is a capacitive coupling between these electrically conductive areas and the measuring fields. The same effect as when a finger approaches such a measuring field is thereby achieved. Thus the properties of fingertips are simulated by the electrically conductive areas.
It is disclosed in WO 2012/038434 A1 to use such a substrate, with electrically conductive areas located thereon, in a banknote.
Whenever the encoding of an item of information by electrically conductive areas is to serve as a security function, there is the problem that the encoding is not supposed to be directly visible; it is supposed to be able to be read exclusively with the aid of the relevant reader, but not to be recognizable on the basis of a simple observation. As soon as the encoding is visually recognizable, there would, namely, be the danger that it could be easily copied.
For this reason, in the state of the art, a larger surface area of the substrate, which contains the electrically conductive areas, or the whole substrate is covered with an opaque (not transparent) cover layer.
Precisely in the case of security elements and documents, by which a security function is to be provided, however, it is desirable if attention is called visually to the security function. Because of the opaque cover layer there are limitations in a design in this regard.